Technical Field
The present disclosure relates to the field of communications, and in particular to a compensation apparatus and method for inter-channel nonlinear damage.
Background
Currently, wavelength division multiplexing (WDM) systems are widely used in communications. As the number of channels in a wavelength division multiplexing system is relatively large and inter-channel nonlinear damage is relatively obvious, the inter-channel nonlinear damage needs to be estimated and compensated.
As the nonlinear Schrodinger equation may well model a nonlinear effect in an optical fiber, in principle, a digital signal processing-based optical coherent detection receiver and constructing an inverse link may compensate for nonlinear damage in an optical fiber transmission link; wherein, attenuation coefficients, dispersion coefficients and nonlinear coefficients in the inverse link and a transmission link are correspondingly inverse to each other. The nonlinear damage here includes in-channel nonlinear damage resulted from a self-phase modulation (SPM) effect and inter-channel nonlinear damage resulted from a cross-phase modulation (XPM) effect. However, as the number of channels in a wavelength division multiplexing (WDM) system is relatively large, in solving the nonlinear Schrodinger equation to which an inverse link corresponds in a digital domain by using a split step Fourier method, information of each channel is needed, steps need to be strictly controlled, thus the complexity of such calculation is unbearable to current chips.
Currently, the XPM effect may be divided into two types by studying and modeling the XPM effect, that is, phase damage and polarization crosstalk. Some existing algorithms can only be addressed to one type of damage for compensation. Finding a method capable of effectively compensating for the two effects of the XPM at the same time is still a hotspot in the current study. An existing method makes an improvement to a conventional method of compensating for XPM damage based on an inverse link; wherein in each step in the split step Fourier method, a signal needs to pass through a nonlinear compensating module and a linear compensating module, and change of a current signal is performed according to an XPM model. Seen from a simulation result, when a dispersion coefficient of an optical fiber is relatively small, the method may expand a step in the split step Fourier method by about 15 times. However, when a split step length is increased to an optical fiber span, a compensation property of the method decreases remarkably. And a usual link is based on a conventional single-mode optical fiber, a dispersion coefficient of which being more than 4 times of the condition supposed in the method, and at this moment, when the step is equal to a length of the span, the performance of the method will decrease further.
It should be noted that the above description of the background is merely provided for clear and complete explanation of the present disclosure and for easy understanding by those skilled in the art. And it should not be understood that the above technical solution is known to those skilled in the art as it is described in the background of the present disclosure.